It has long been known that the high radiation environment of outer space, especially space beyond Low Earth Orbit (LEO), is a harsh environment that can quickly degrade the performance of Commercial Off-The-Shelf (COTS) electronics. As used herein, “Deep Space” means the region of space above Earth's radiation belts, i.e., roughly above 36,000 km in altitude above the Earth's surface. COTS electronics refers to electronics that are not specially “radiation-hardened” by design. The space environment in Deep Space is known to provide a background dose rate of radiation which is reasonably low, comparable to that in LEO. Such background dose rate of radiation is generally tolerable by COTS electronics for periods of at least several years. However, the radiation environment in Deep Space is punctuated by short periods of very high dose rates during Solar Proton Events (SPEs). A SPE can include such solar events as solar flares or coronal mass ejections (when their path intersects the spacecraft), or any other event where the number of high energy protons impacting the spacecraft suddenly and dramatically increases for a short period of time.
High dose rates of high-energy protons can be very damaging to electronics, particularly to COTS electronics, both causing rapid “aging” of some types of electronics due to Total Ionizing Dose effects, and causing Single Event Effects such as memory bit-flips, and latchups and burn-throughs of transistors. Almost all of the severe damage expected to happen to COTS electronics caused by radiation in the space environment in Deep Space is expected to happen during the few, brief, SPEs that a spacecraft would encounter during its mission. Accordingly, if the spacecraft electronics can be protected during SPEs, the likelihood that the spacecraft electronics will be safe for the duration of a multi-year mission increases.
Traditionally, this problem has been overcome by using at least one of: radiation shielding, redundant systems and specially designed and manufactured, radiation hardened electronics. Each of these has significant drawbacks. Radiation shielding is heavy and can greatly increase the cost of launching a spacecraft as well as increase the propellant required to manoeuver once in space. Redundant systems increase cost and weight as well as design complexity. The extensive testing and low production numbers of components for radiation hardened electronics leads to much higher costs on a per-part basis, and much longer development cycles due to the generally extremely long delivery lead-times for this class of part. Generally, radiation hardened electronics are also several years behind the current generation of COTS electronics, leading to larger and heavier form factors, greater power consumption and generally less capable devices.
Any spacecraft would benefit from the ability to use COTS electronics rather than specially designed and built radiation hardened electronics, but the benefit is especially significant for micro- or nano-spacecraft, where components must be small, bulky shielding is not feasible and low cost is a requirement. The ability to use COTS electronics on board a spacecraft has been shown, in many microsatellite, nanosatellite and Cubesat missions flown in LEO, to provide several benefits as compared to those using higher-grade parts. Such benefits include lower costs (since mass produced components can be used), shorter development cycles (since acquisition and testing of commercially produced electronics can be done quickly), and smaller as well as lighter form factors (since current generation electronics are smaller, often have more functions integrated onto a single chip and use, power more efficiently).